INDUSTRIAL PROGRESS DURING THE YEAR 1876. Ixix 



Bunsen has given some results obtained in his laboratory by 

 Hillebrand and Norton on the electrolytic preparation of the metals 

 contained in the mineral cerite. About forty grammes of the elements 

 cerium, lanthanum, and didymium were obtained in this way. 



Kerr has been led from theoretical considerations to the discovery 

 of a new relation between electricity and light. He has proved 

 that dielectrified media are doubly refractive during the charge. 

 The media employed were glass, resin, and quartz. The results prove 

 that dielectrified resin acts as if extended along the lines of force, while 

 dielectrified glass and quartz act upon the transmitted light as if 

 they were compressed along the lines of force. 



Colladon has published an extended research on the efiect of 

 lightning on trees, in which he gives the results of investigations on 

 poplars, oaks, elms, pears, firs, grape-vines, chestnuts, and walnuts. 

 The conductivity of poplar, he observes, is such as to make it of serv- 

 ice as a lightning-rod, and he recommends connecting the base of 

 these and of other tall trees with permanently moist earth if possi- 

 ble a watercourse by means of a metallic rod. 



Schaack has given in a recent memoir his views upon the con- 

 struction of lightning-arresters at present used for telegrajDh lines. 

 He proposes to replace these by a simple trough of water, made of 

 metal and connected to earth, through which the wire (a fine spiral 

 of silk-wound German-silver wire covered with a thin coating of 

 rubber) which connects the register with the line passes. The earth 

 connection from the register is made to the metal of this trough. A 

 discharge of lightning would melt the small wire and escape to 

 earth, leaving the instruments uninjured. 



